Pulse generator apparatus

ABSTRACT

A pulse generator for providing pulse sequences in which the individual pulses are of different durations, wherein a multistable device having a plurality of different states determines the order of the pulses of the sequences, wherein a multivibrator steps the multistable device through its sequence of states, and wherein the multistable device is coupled to the multivibrator to vary its controlling time constants during certain of such states.

United States Patent Bankovic 1 June 6, 1972 [54] PULSE GENERATOR APPARATUS 3,256,488 6/1966 St. John et a]. ..328/6l 3,317,743 5 1967 R ...328 63 X [721 Invent Amnmfie Helm", 3 381 227 441968 Kgszfl ic ..32848 x [73] Assignee: Societe lndustrielle Honeywell Bull, Paris,

France Primary Examiner-John S. Heyman AttomeyLewis P. Elbinger, Fred Jacob and Ronald T. Reil- [22] Filed: Apr. 6, 1970 ing [21] Appl. No.: 25,999 [57] ABSTRACT 1 A pulse generator for providing pulse sequences in which the Foreign Application Priority Data individual pulses are of different durations, wherein a multistable device having a plurality of different states deter- Apr. 9, 1969 France ..6910934 mines the order of the pulses of the sequences wherein a tivibrator steps the multistable device through its sequence of [52] U.S.Cl ..307/265,307/247, 307/292, states, and wherein the mumstable device is coupled to 307/283, 307/255 multivibrator to vary its controlling time constants during cer- [51] Int. Cl ..H03k 1/18, H03k 17/60 tain of such states. [58] Field of Search ..328/48, 60, 61, 63; 307/247, 307/265, 255, 288, 292

[56] References Cited 6 Chins, 4 Drawing Figures UNITED STATES PATENTS 3,188,486 6/1965 Favin ..328/61 X l l i r l I I I '1 I I 1 l I l l I I l5 Q L14 i6 l 1 A? %d8 D 11 l RX RY l l J X Y I Lib, L J 5 MULTIVIBRATOR 530 530 17 Q-41 12 START-STOP DEVICE PATENTEDJUH 6 I972 SHEET 20F 3 1 Z5 39 E3D Gib/v.0.

INVENTOR $461. MEMO-01c ATTORNEY PULSE GENERATOR APPARATUS BACKGROUND OF THE INVENTION This invention relates to improvements in pulse generators and more particularly to pulse generators intended for generating sequences of pulses having different durations.

The pulse generator of this invention has been designed to be incorporated in a punched-card processing machine under control of a keyboard. In some of these machines the cycles of operation are the result of a time base constituted of contacts controlled by earns, the latter being attached to a common shaft in continuous rotation. Assuming that the instant of striking of a key of the keyboard is purely random, it can be proven that there is an equivalent loss of time, on the average, of a half cycle of operation before an effective cycle of operation is triggered. This results in a significant reduction of performance of the machine.

If it is desired to replace such a time base, which furnishes one or more pulse sequences of different durations, by electronic means, an apparatus which is costly to fabricate and to place into operation has been required in the past. Thus, the present invention is directed to furnishing a generator of pulses of different durations, which can be rendered operative without delay; i.e., from the beginning of a control signal, and which is economical and is simple to adjust.

For the purpose of brevity, and although it is not customary usage, the term phase will be employed herein for the duration of a pulse as well as for the time of an interval between two successive pulses.

Therefore, the object of this invention is to provide a pulse generator for use in a machine for processing punched cards under control of a keyboard.

Another object of the invention is to provide such a pulse generator which can be modified rapidly in order that it be capable of generating pulses in different sequences; i.e., that the order of the pulse phases of different durations of a sequence can be modified according to requirements, although the total duration of a sequence is the same for all possible sequences, at least with only a possible minor adjustment.

Another object of the invention is to furnish a pulse generator of the type described above which can be controlled by a control signal whose duration does not necessarily have to be fixed in a rigorous and precise manner.

It is obvious that the use of such a pulse generator is not limited to the type of machines indicated previously but, on the contrary, its advantages will be recognized in many other domains of application, particularly where there is a need for a generator which can deliver sequences of various types of pulses of different predetermined durations.

It is to be understood that the designation of sequence of pulses with phases of different durations is applicable to the case where, for example, in the four phases of a sequence, only one has a duration different from that of the other three, to the case where these four phases are all of unequal duration, and to all the intermediate cases.

SUMMARY OF THE INVENTION The concept of this invention consists of uniting a multivibrator circuit and a multistable device by means of reciprocal connections such that the signals available at the multivibrator outputs induce changes of state in the multistable device, which is capable, in turn, of modifying the time constant of at least one time constant network of the multivibrator, during at least one of the phases of the sequence of pulses.

Consequently, according to the invention, the pulse generator comprises a multistable device including at least first and second flip-flop circuits, and a multivibrator of the type having two R-C time constant networks and having two corresponding complementary outputs, such pulse generator being characterized in that, in the multistable device each flip-flop is provided with two separate control inputs, with one common control input, and with two complementary outputs. Connections are provided between the outputs of each of the flipflops and the separate inputs of the other flip-flop for determining the order in which the stable states of the multistable device follow each other. The multi-vibrator is provided with at least one access terminal from which one of the networks can have its time constant modified. The pulse generator is provided with a start-stop device connected to the mulu'vibrator for assuring either the state of rest of the generator, or its operating state. A first set of connections for coupling at least said access terminal of the multivibrator to one output of one of the flip-flops and a second set of connections for coupling each multivibrator output to the common input of a respective flip-flop of the multistable device is provided. These connec tions are established in such a manner that during the operating state each output of the multivibrator can generate two pulses in the course of at least one pulse sequence composed of four phases, wherein at least one of these phases cor responds to the modified time constant of a time constant network of the multivibrator.

According to other characteristics of the invention, the multivibrator is provided with a supplimentary access terminal from which another network can have its time constant modified. The first set of connections includes a connection for coupling this supplementary access terminal of the multivibrator to one output of the other flip-flop in such a manner that, in the sequence of pulses, two phases correspond respectively to the modified time constant of each of the time constant networks of the multivibrator.

Preferably, the time constant of a network is modified by connecting an additional resistance in parallel with the normal resistance of the network.

BRIEF DESCRIPTION OF THE DRAWING FIG. 3 is a schematic diagram of the start-stop device of I FIG. 1; and,

FIG. 4 is a timing diagram of waveforms available at certain points in the pulse generator circuits.

DESCRIPTIONOF THE PREFERRED EMBODIMENT The pulse generator of FIG. 1 comprises essentially a multistable device 10, a multivibrator circuit 11, and a startstop device 12. The multistable device comprises a first bistable circuit (flip-flop) BA and a second flip-flop BB, with connections which are apparent as being-those of a binary counter of two stages. Flip-flop BA is provided with two separate inputs EO and El, with one common input EA, and with two complementary outputs SA and SA. Flip-flop BB is provided with two separate inputs E0 and E], with one common input EB, and with two complementary outputs SB and SB. The interconnections being symmetrical, it is sufficient to observe that output SA of flip-flop BA is connected to input E1 of flipflop BB.

It is known that with most flip-flops the presence of a voltage of high level, to which is attributed the binary value l," on one of the flip-flop outputs corresponds to a first state of conduction of the circuit, and that the presence of the voltage of high level on the other output corresponds to the second state of conduction, complementary to the first state. Therefore, it can be said that the multistable device possesses four stable states, which are designated as AB, AB, AB, and AB. By way of example, in the state AB, outputs SA and SB are found at the high voltage level, whereas outputs SA and SB are found at a low voltage level.

In the rectangle symbolizing multivibrator 11, there is shown only those components related the operation in accordance with the invention. Thus, two resistors 246 and 24D form, with capacitor C, two time-constant networks. Additionally, in the block of multivibrator 11 are two additional resistors RX and RY, which have ends connected to the respective junction points X and Y. The other ends of these resistors are connected to access terminals, such as terminals 186 and 18D. In the example shown, a connection 13 is provided between access terminal 186 and output SA of flip-flop BA, and a connection 14 between access terminal 18D and output SB of flip-flop BB. It follows that when multistable device assumes either state AB or AB, the resistor RX is effectively in parallel with resistor 246, and that when the multistable device assumes either state AB or AB the resistor RY is effectively in parallel with resistor 24D. I

Multivibrator '1 1 comprises two output terminals S6 and SD for delivering complementary series of pulses to one or more utilization devices, not shown. In the example considered, a connection 15 couples terminal S6 to the common input EA of flip-flop BA and a connection 16 couples terminal SD to the common input EB of flip-flop BB. As connections 13-16 may be modified, for reasons which will be explained hereinafter, they have been represented by broken lines in order to distinguish them from the other fixed connections.

Multivibrator '11 is provided with two control terminals E36 and E3D, of which one can be coupled by a connection 17 to a terminal 41 of start-stop device 12. Device 12 is adapted for maintaining the pulse generator inoperative or for placing it in service, depending on the signals applied to its inputs.

Although multivibrator 11 can be of any known type suitable for employment as presently foreseen, it is preferable that it be arranged in accordance with that described in the French Pat. application No. 6,902,009, filed Jan. 31, 1969, for Improvements in Multivibrator Circuits, which corresponds to US. Pat. application Ser. No. 6,682, filed Jan. 29, 1970, and assigned to the same assignee as the instant invention.

The schematic diagram of one embodiment of multivibrator 1 1 is shown in the lower part of FIG. 2. It is supplied from two terminals 30 and 31, assumed to be coupled to the terminals of a direct voltage source, not shown, which furnishes to terminal 30- a voltage +V1, which preferentially is stabilized, although this is not always essential. A voltage divider comprising resistors 21, 22, and 23 in a branch between terminals 30 and 31 provides for obtaining an adjustable reference voltage at a point +VR. It is evident that the circuit of the multivibrator is composed of two branches of identical structure. For example, in the left branch is disposed a resistor 246 connected between terminal 30 and the emitter of a first PNP transistor T16. The base of transistor T16 is connected to terminal 30 through a resistor 266, to the point +VR through a diode D16, and to the collector of a second transistor T26 through a diode D26. Transistor T26, a silicon NPN transistor, has its emitter directly connected to terminal 31 and its collector directly connected to output terminal SG. In addition, a resistor 29G connects terminal 30 to the collector of transistor T26. The base of transistor T26 is connected to terminal 30 through a resistor 286 and is connected to the collector of a third NPN transistor T36. Transistor T36, of which the emitter is connected directly to terminal 31, has its base connected directly to the collector of a transistor TlD of the other branch, as well as to control terminal E36. The base of transistor T36 is also connected to terminal 31 through a resistor 256.

A capacitor C has one of its plates connected to a junction point X between resistor 246 and the emitter of transistor T16, and its other plate connected to a junction point Y between resistor 24D and the emitter of transistor TlD. Capacitor C forms, with each of resistors 246 and 24D a separate time constant network. Resistors RX and RY, mentioned above, each has One end thereof connected to an access terminal, such as respective terminals 186 and 18D.

FIG. 2 shows the connections 13-16 mentioned previously in relation to FIG. 1. The schematic diagrams of flip-flops BA and BB, which are identical, are shown in the upper portion of FIG. 2. Each flip-flop is of simple and conventional construction and is supplied by the same direct voltage source as multivibrator 11. Each flip-flop is of symmetrical structure. Therefore a branch of flip-flop BA comprises, for example, a PNP transistor T46. The collector current of transistor T46 flows through a diode D56 and a resistor 196. The separate input E0 is connected to the base of transistor T46 through a diode D36 and a resistor 426. The polarity of the voltage on the base of transistor T46 is determined primarily by a voltage divider composed of resistor 436, of which one end is connected to a voltage source furnishing a voltage +V2, greater than +V1, and a resistor 446, of which one end is connected to the junction between a diode D5D and a resistor 19D, of the other branch. The collector of transistor T46 is connected to output temiinal SA. The common input EA is connected to two resistors 456 and 45D, of which, for example, one end of resistor 456 is connected to the junction point between diode D36 and resistor 426. The interconnections between the out-v puts of one flip-flop and the separate inputs of the other flipflop correspond to those mentioned with reference to FIG. 1.

Assume now, that in the state of rest, or arrest," of the pulse generator, flip-flop BA is in state A; i.e., with transistor T46 conductive and transistor T4D non-conductive, or cut off. In this condition, a high voltage level (slightly less than +Vl) is present on output SA, whereas output SA has low voltage level, a level between +V1 and 0 volts. These levels of voltage are inverted when flip-flop BA is in the opposite state A. During the above-mentioned arrest state of the pulse generator, flip-flop BB is in state B.

The start-stop device 12, FIG. 3, is supplied from the same sources of voltage as the flip-flops of the multistable device 10. Start-stop device '12 comprises the transistors T5 and T6, which are respectively of the PNP and NPN types. The collector current of transistor T5 flows through the resistors 32 and 33, connected in series, and through the base-emitter path of transistor T6. A voltage divider having resistors 34, 35, and 36 is connected between the terminals receiving the voltages +V2 and 0 v. A logic circuit 37, comprising three diodes, such as diode D4, is coupled to the junction of resistors 35 and 36. In logic circuit 37, a first input 38 is coupled to output SA of flip-flop BA, a second input 39 is coupled to output SB of flipflop BB, and a third input 40 is coupled for receiving a control signal designated COM" from a control member, not shown. This control member can be of any type convenient for fumishing a two-level signal, wherein one level must be low for conditioning the arrest of the pulse generator and wherein the other level must be high and continue sufficiently long to enable the operation of the pulse generator during the desired time, as will be explained hereinafter.

During the state of arrest of the pulse generator, the three signals received by inputs 38-40 of logic circuit 37 must be at the low level in order that all three diodes are non-conductive, thereby permitting the base current of transistor T5 to flow through resistors 35 and 36. Transistors T5 and T6 are then conducting at saturation. The collector of transistor T6 is connected to a terminal 41, which is coupled through connection 17 to terminal E36 of multivibrator 11, FIG. 2. When transistor T6 is saturated, the base-emitter voltage of transistor T36 is insufficient for it to be conductive and, therefore, transistor T36 is cut off. This holds the multivibrator in a predetermined rest state.

Logic circuit 37 constitutes an OR-gate relative to positive signals, or signals of high level. Thus, when the signal COM transfers to a voltage level nearly equal to +V1, the diode connected to input 40 becomes conductive, thereupon interrupting the base current of transistor T5, which becomes cut off and forces the cut off of transistor T6. From this instant, transistor T36 of the multivibrator is enabled to become conductive, thereby permitting the start of operation of the pulse generator, as will be explained in detail, hereinafter.

It will be assumed to start that the pulse generator has been arranged for generating one or more pulse sequences of an invariant type, each of these sequences being composed of two pulses issuing in the course of the four successive phases forming a cycle of operation, these phases occurring in a circuit wherein the connections 13-17 are fixed.

The operation of multivibrator 11 will be explained first without following its effect on multistable device 10. It will be assumed, in the embodiment shown, that the four phases of a sequence all have different durations and that each sequence corresponds to a cycle of operation of duration detemtined by component values. By way of example, the following values are assumed: resistors; 24G= 4.3 kilohms (or 4.3 K), RX= 16 K, 24D 6.2 K; RY 27 K; capacitor C 2.2 rnicrofarads; and +V1 16 volts and +V2 26 volts.

During the state of rest, or arrest, of the pulse generator, multistable device is in the state AB. The signal COM is at its low level (FIG. 4), and transistors T5 and T6 of start-stop device 12 are saturated. As transistor T6 is equivalent, in its saturated state, to a closed switch, transistor T36 is cut off, thereupon forcing on the multivibrator its rest state, or inoperative state. The other resistors of the multivibrator are determined such that, in this state of rest, transistors T26, T16, and T3D are saturated, transistor T2D is non-conductive or cut off, and transistor TlD is moderately conductive, its collector current being absorbed principally by the collectoremitter path of transistor T6 (FIG. 3) and its base current flowing through diode DlD, which similarly carries the current provided by resistor 26D. The voltages on outputs S6 and SD are respectively at their low and high levels. Capacitor C is charged to a voltage which differs slightly from +VR, its plate connected to point X being negative relative to that connected to point Y.

When at time t0 the signal COM transfers to its high level, transistor T36 is rendered conductive, as indicated previously, and its saturation conduction forces the cut off of transistor T26, of transistor T16, and then of transistor T3D. The cut off of transistor T3D forces the saturation conduction of transistors T2D and TlD. The voltagelevels on outputs S6 and SD invert from their previous values. The abrupt drop of voltage of point Y is transmitted by capacitor C to point X, which attains a minimum voltage point very much lower than 0 v., further reinforcing the cut off of transistors T16 and T26. From this moment, capacitor C commences to discharge, the discharge current flowing through resistors 246 and RX in parallel, through capacitor C, and through transistor TlD. Since flipflop BA is in state A, transistor T46 is saturated and the low resistance of its emitter-collector path is negligible in relation to the 16 K of resistor RX. Capacitor C then recharges in the opposite sense since the voltage at point Y remains stable until the end of the first phase Pl.

At time t1 the potential at point X reaches a positive threshold voltage at which some base current of transistor T16 can flow through diode D16 toward point +VR. Because of the amplification of the current carried by transistor T16, transistor Tim is rendered conductive, forcing the cut off of transistors T2D and TlD, while the voltage on output SD returns to its high level. Transistors T16 and T26 are driven to saturation conduction, point X is subjected to a negative voltage excursion, and point Y is driven to the minimum voltage point mentioned above. The voltage on output S6 drops to its lower level, while capacitor C commences to discharge through resistors 24]) and RY in parallel, because flip-flop BB is in state B during phase P2 and its transistor T46 is saturated. The operation of the multivibrator proceeds in the same manner through the following phases, a change of its state of conduction being produced at each of times 13, t4, and so on.

Consider now the action of multivibrator 11 on multistable device 10. Multistable device 10 is in state AB during the arrest state of the pulse generator. At time t0, the drop of voltage at output SD to the low level triggers, through connection 16 to common input EB, the transfer of flip-flop BB to its state B. Transistors T46 and T4!) become respectively conductive and cut off. This transfer results from the fact that diode D36 of flip-flop BB was non-conducting because of the low voltage level existing on output SA of flip-flop BA. The raising of the voltage level on output 56 does not have an effect on flip-flop BA which remains in state A.

By virtue of the control exercised by diodes D36 and D3D of flip-flops BA and BB at time :1, when output S6 of multivibrator l l returns to its low level, only flip-flop BA changes state, transferring to state A. At time t2, when output SD returns to its low level, only flip-flop BB is triggered, returning to its state B. At time t3, when output S6 returns again to its low level, only flip-flop BA is triggered, returning to its state A. The multistable device 10 then represents the same state AB which it assumed before the start of operation of the pulse generator. It maybe noted that during phase P2 diode D56 of flip-flop BA is polarized to be non-conductive. Because of this, direct coupling of resistor RX with the junction between resistors 196 and MD of flip-flop BA is prevented, whereas without this precaution the voltage at point X would vary.

If, as shown in FIG. 4, the signal COM is not interrupted until after time :4, which marks the end of the first cycle of operation 0C1, as for example at time :51, the pulse generator continues to operate during a second cycle, such as 0C2. This is because during the time-intervals extending from t0 to t3 and from 14 to t7 there is at least one flip-flop output among SA and SB at the high voltage level, which independently of control signal COM is sufficient to assure the cut off of transistors T5 and T6 of start-stop device 12 (FIG. 3), thereby permitting the continued operation of the pulse generator. On the line designated VAL (FIG. 3), the high level represents the cut off state of transistor T6, during which transistor T36 is conductive. However, in the embodiment described, at time :7 multistable device 10 assumes the state AB. Since the signal COM has been interrupted previously, inputs 38, 39, and 40, FIG. 3, of logic circuit 37 all receive a low level of voltage, causing the saturation of transistors T5 and T6. Capacitor C, FIG. 2, at this time discharges and then recharges, so that the voltage at point Y returns to its high level, which it attains at time t8 (FIG. 4). At this moment, since transistor T36 is held cut off, the operation of the pulse generator is halted.

The multivibrator disclosed presents numerous advantages compared to multivibrators of other types. First, it generates its two pulse outputs with steep leading edges, even if the pulses are of relatively long duration. Further, it is economical to fabricate and to place into operation, because the single regulation 23 of reference voltage +VR pennits compensating the tolerances of the capacitance of the single capacitor C and obtaining, as well, the desired period of the cycle of operation. The relationships of the durations of the four phases of a cycle of operation, or of a pulse sequence, are defined by the resistors of the time constant networks, which are not very costly, yet are of sufficiently high precision. Furthermore, the generator readily accepts a control signal of an imprecise duration. For example, as shown in FIG. 4, the signal COM can be interrupted at time r41, a time sufficiently after the start of the second cycle of operation 0C2, that flip-flop BB has securely assumed its new state of conduction. Furthermore, the signal COM can be prolonged until time r71, a time sufficiently ahead of time t8 that transistors T5 and T6 of the startstop device have had time to become saturated before time 18.

Stated this function differently, each time that the pulse generator is placed under voltage, the action of the start-stop device is such that the pulse generator, after passing through one or more of the phases of a cycle of operation, terminates its sequence and is placed automatically in the non-operating state, since it is assumed that the control signal COM is absent at this time.

As is known, the duration of a phase of conduction of a branch of the multivibrator is equal to KRC, K being a coefficient which is constant once the level of voltage +VR relative to +Vl has been adjusted, and C being the invariant capacitance of the single capacitor C. During the first phase P1 of a sequence of pulses, the duration of the phase is determined by R 340K, resulting from resistors 246 and RX in parallel. During the second phase P2, the duration is determined by R 5.05 K, resulting so... resistors 24D and RY in parallel. During the third phase P3, the duration is determined During the fourth phase P4, the duration is determined by R= 6.2 K, which is that of resistor 24D alone, resistor RY not participating, for similar reasons to those set forth relative to phase P3. For example, with the resistance values indicated herein, phases P1, P2, P3, and P4 can have durations of 7.5, 10.5, 9, and 13 milliseconds respectively, which result in the period of the operating cycle being 40 milliseconds.

The sequence of pulses illustrated in FIG. 4 can be symbolized by means of the following: GR, DR, GN, DN: wherein G denotes that the duration of the phase depends on resistor 24G, shunted or not, D denotes that the duration of the phase depends on resistor 24D, shunted or not, N denotes a normal duration (resistors 240 or 24D not being shunted), and R denotes a reduced duration (resistors 24G or 24D being shunted). The notations "normal" and reduced" are purely arbritrary. V g

The pulse generator is capable of generating four difi'erent pulse sequences in a certain order and four different pulse sequences in the inverse order by modifying certain of the couplings effected by connections 13-17 and by choosing for themultistable device a convenient state of conduction for arresting the pulse generator.

The four first sequences are defined as f follows:

GR GR GN GN DR DN DR DN IA ID IC ID GN GN GR GR DN DR DN DR The four sequences of inverse order are defined as follows:

' DN DR ON ON GN GR GR A "B "C "D DN DR DN DR GR GR GN GN I For example, to obtain the sequences 13 through ID, terminal 41 of start-stop device 12 remains connected to terminal ESG and the state, of rest of multistable device 10 is the same as that indicated above, namely AR: For Obtaining sequence 18, resistor .RX is connected to terminal SA of flipflop BA and resistor RY is connected to terminal SE of flip flop BB. For obtaining sequence lC, resistor RX is connected to terminal SA and resistor RY to terminal SB. For obtaining sequence ID resistor RX is connected to terminal SA and resistor RY to terminal SE.

For obtaining sequences "A through D, the above-indicated connections between resistor RX and RY and the outputs of the multistable device repeat in this instance. The only consistent difference is that the state of rest of the multistable device is now state AB and that terminal 41 of starbstop device 12 is coupled by connection 17 to terminal ESD of the multivibrator. Moreover, of the inputs 38 and 39 of logic circuit 37, one must be connected to output SA of flip-flop BA and the other to output SE of flip-flop BB.

The eight sequences indicated above can also be obtained by choosing the states of rest of the multistable device inverse to that indicated; i.e., AB and AF, and by modifying the connections accordingly.

There exist still other possible combinations which may be responsive to certain requirements. For example, by eliminating one of the shunt resistors RX or RY, sequences of pulses can be obtained in which only one of the phases will be of reduced duration and in which clearly, at least two phases will be of the same duration. This is the same as, for example,

omitting connection 14 between terminal 18D and any output of multistable device 10, whereby'resistor RY is effectively eliminated. The following four sequences can be obtained by this technique:

GR GN DN DN DN DN GR GN GN GR DN DN DN DN GN GR Further combinations can be provided, particularly in the case where it is desirable that the generator be able to deliver sequences of pulses composed of more than four pulse phases. In particular, there can be provided one or more supplementary shunt resistors asociated with the multivibrator, and the multistable device must then comprise more than two stages, with possibly logic means for limiting the total number of stable states or for obtaining a succession of stable states different from that in FIG. 4. 1

It is apparent, that in accordance with the rapidity with which it is desired to effect the changes of connections indicated above, different means can be employed. For example, there can be provided cables with plugs which are plugga ble into sockets of a connectionpanel, switches for manual control, or the more rapid electrical or electronic switches.

From that which has been shown of modifying the resistors of the time constant networks of the multivibrator, it is clear that other means possibly can consist of replacing a resistor, such as resistor 740 for example (FIG. 2), with two resistors of appropriate values in series. Their point of junction will then be coupled by connection 13 to output SA of flip-flop BA. However, it cannot be considered that one of these resistors will be short-circuited entirely, because the resistance of the emitter-collector path of saturated transistor T40 of flip-flop BA is not negligible.

Because much that has been described in the preceding and shown in the drawings is characteristic of the invention, it is evident that one skilled in the art can produce all modifications of form and detail deemed useful without departing from the scope of the invention.

I claim:

1. A pulse generator having a multistable device including at least a first and a second flip-flop and a multivibrator circuit of the type having two R-C time constant networks and two corresponding complementary outputs, wherein the improvement comprises: each flip-flop of the multistable device being provided with two separate control inputs, with one common control input, and with two complementary outputs; connections being provided between the outputs of each of said flipflops and the separate inputs of the otherflip-flop appropriate for determining the order of succession of the stable states of the multistable device; said multivibrator circuit being provided with at least one access terminal from which one of said networks can have its time constant modified; a start-stop device connected to said multivibrator circuit for assuring either a state of rest thereof or an operating state; a first set of connections for coupling at least said access terminal of said multivibrator circuit to an output of one of said flip-flops and a second set of connections for coupling each output of said multivibrator circuit to the common input of a respective one of said flip-flops, said connections being arranged such that each output of the said multivibrator can generate, during the operating state, two pulses in the course of at least one pulse sequence composed of four phases, in which at least one of said phases corresponds to the modified time constant of a time constant network of said multivibrator circuit.

2. The pulse generator of claim 1, wherein said multivibrator circuit is provided with an additional access terminal from which the other one of said networks can have its time constant modified, said first set of connections including a connection for coupling said additional access terminal of said multivibrator circuit to an output of the other one of said flipflops, such that during said pulse sequence two phases correspond respectively to the modified time constants of each of the time constant networks of said multivibrator circuit.

3. The pulse generator of claim 1, wherein said multivibrator circuit comprises two branches, each branch comprising a first transistor, a second complementary transistor, and a third transistor of the same conductivity type as said second transistor, wherein a resistor is connected to the emitter of said first transistor, a capacitor, said resistor and capacitor constituting a time constant network, and wherein there is further provided additional resistance connected between said emitter and said access terminal by which the normal time constant of said network can be reduced when the flip-flop connected to said access terminal is in a predetermined state.

4. The pulse generator of claim 3, wherein said start-stop device comprises a switch member connected between the base and the emitter of said third transistor of one of said two multivibrator circuit branches, whereby a predetermined rest state of said multivibrator circuit is determined.

5. The pulse generator of claim 4, wherein said switch member is constituted of the emitter-collector path of an additional transistor and wherein the state of conduction of said additional transistor is controlled by a logic circuit of which one input receives a control signal and the two other inputs are each connected to an output of a different flip-flop of the multistable device, according to the state of rest selected for the pulse generator.

6. Apparatus for generating a sequence of n pulses wherein at least one of said pulses is of difierent duration than the other pulses of said sequence, comprising: a multistable device controllable in response to a succession of control signals received thereby for operating successively in n different sta ble states, n being at least 4, said multistable device delivering an output signal when said multistable device is operating in a predetermined one of said n states, a control signal generator for generating said succession of control signals, said control signal generator comprising a plurality of time-constant networks for determining the intervals between adjacent ones of said control signals, means coupling said control signal generator to deliver said control signals to said multistable device, and means for transmitting said output signal to said control signal generator for modifying the time constant of one of said networks during said one state. 

1. A pulse generator having a multistable device including at least a first and a second flip-flop and a multivibrator circuit of the type having two R-C time constant networks and two corresponding complementary outputs, wherein the improvement comprises: each flip-flop of the multistable device being provided with two separate control inputs, with one common control input, and with two complementary outputs; connections being provided between the outputs of each of said flip-flops and the separate inputs of the other flip-flop appropriate for determining the order of succession of the stable states of the multistable device; said multivibrator circuit being provided with at least one access terminal from which one of said networks can have its time constant modified; a start-stop device connected to said multivibrator circuit for assuring either a state of rest thereof or an operating state; a first set of connections for coupling at least said access terminal of said multivibrator circuit to an output of one of said flip-flops and a second set of connections for coupling each output of said multivibrator circuit to the common input of a respective one of said flip-flops, said connections being arranged such that each output of the said multivibrator can generate, during the operating state, two pulses in the course of at least one pulse sequence composed of four phases, in which at least one of said phases corresponds to the modified time constant of a time constant network of said multivibrator circuit.
 2. The pulse generator of claim 1, wherein said multivibrator circuit is provided with an additional access terminal from which the other one of said networks can have its time constant modified, said first set of connections including a connection for coupling said additional access terminal of said multivibrator circuit to an output of the other one of said flip-flops, such that during said pulse sequence two phases correspond respectively to the modified time constants of each of the time constant networks of said multivibrator circuit.
 3. The pulse generator of claim 1, wherein said multivibrator circuit comprises two branches, each branch comprising a first transistor, a second complementary transistor, and a third transistor of the same conductivity type as said second transistor, wherein a resistor is connected to the emitter of said first transistor, a capacitor, said resistor and capacitor constituting a time constant network, and wherein there is further provided additional resistaNce connected between said emitter and said access terminal by which the normal time constant of said network can be reduced when the flip-flop connected to said access terminal is in a predetermined state.
 4. The pulse generator of claim 3, wherein said start-stop device comprises a switch member connected between the base and the emitter of said third transistor of one of said two multivibrator circuit branches, whereby a predetermined rest state of said multivibrator circuit is determined.
 5. The pulse generator of claim 4, wherein said switch member is constituted of the emitter-collector path of an additional transistor and wherein the state of conduction of said additional transistor is controlled by a logic circuit of which one input receives a control signal and the two other inputs are each connected to an output of a different flip-flop of the multistable device, according to the state of rest selected for the pulse generator.
 6. Apparatus for generating a sequence of n pulses wherein at least one of said pulses is of different duration than the other pulses of said sequence, comprising: a multistable device controllable in response to a succession of control signals received thereby for operating successively in n different stable states, n being at least 4, said multistable device delivering an output signal when said multistable device is operating in a predetermined one of said n states, a control signal generator for generating said succession of control signals, said control signal generator comprising a plurality of time-constant networks for determining the intervals between adjacent ones of said control signals, means coupling said control signal generator to deliver said control signals to said multistable device, and means for transmitting said output signal to said control signal generator for modifying the time constant of one of said networks during said one state. 